“It's a simple matter of mathematics.”
“My mathematics is simple: one plus one = one.”
“The formulation of the problem is often more essential than its solution, which may be merely a matter of mathematical or experimental skill.”
“If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.”
“Then suddenly, he was struck by a powerful but simple little truth, and it was this: that English grammar is governed by rules that are almost mathematical in their strictness!”
“It's not that simple or clear-cut - and I wonder if it ever is when it comes to matters of the heart.”